Pharmaceutical composition for emergency contraception

ABSTRACT

The invention relates to pharmaceutical compositions for emergency contraception, to the use of levonorgestrel in combination with COX inhibitors for the preparation of pharmaceutical compositions for the stated purpose, and to a method for preparing these pharmaceutical compositions.

The invention relates to pharmaceutical compositions for emergencycontraception (also known as the “day after pill”), to the use oflevonorgestrel in combination with COX inhibitors for the preparation ofpharmaceutical compositions for the stated purpose, and to a method forpreparing these pharmaceutical compositions.

Various devices and pharmaceutical compositions, for example the condom,pessary, intrauterine pessary and the various monophasic or multiphasicoral contraceptives, are available for preventing unwanted pregnancy.However, despite the wide variety of methods of contraception, sexualintercourse is in many cases performed entirely without protection, evenwhen pregnancy is not wanted.

Such a situation arises, for example, in rape cases or when thecontraceptive device, e.g. condom, is damaged. If ovulation is preventedin these cases, or if fertilization is prevented once ovulation hastaken place, then pregnancy can be avoided. For this purpose, emergencycontraception has to performed soon after sexual intercourse, at thelatest within 72 hours.

This type of emergency contraception can be performed not only byintrauterine contraception with copper-containing intrauterine pessaries(e.g. Nova T®), but also in particular using emergency contraceptivepills (ECPs), where a distinction is made between two types: (a) EPCsthat contain both estrogens and also gestagens, and (b) the more recent“progestin only” pills, which contain only gestagen as the activeconstituent.

The more recent “progestin only” ECPs have by now largely supplanted theolder combined ECPs, since they are more efficient and cause fewer sideeffects. However, the contraceptive efficacy of these preparations toois considerably below the efficacy that is achieved by regularadministration of an oral contraceptive. Thus, in an article entitled“Understanding Contraceptive Failure” [Best Practice & Research ClinicalObstetrics and Gynaecology 23 (2009) 199-209], Trussel et al. reportthat, in different studies, the effectiveness of LNG-based EPCs was onlybetween 59 and 94%.

The mechanism of action of these preparations containing estrogen andgestagen, and also of the preparations that exclusively containgestagen, has been investigated in a large number of studies. Thesestudies confirm that the mechanism of action lies in ovulation beinginhibited or delayed^(1, 2, 3, 4).

This delay in ovulation explains the efficacy of ECPs if they are takenduring the first half of the cycle, i.e. before ovulation.

Studies have also examined the question of whether EPCs have an effecton avoiding pregnancy even after ovulation. A comprehensive review ofthis question is provided by J. Trussell and E. G. Raymond in theirarticle “Emergency Contraception: A Last Chance to Prevent UnintendedPregnancy” published in March 2009. However, in view of the differentand in some cases contradictory (study) results, the authors come to theconclusion that the question of whether ECPs can prevent pregnancy evenafter fertilization will never be resolved.

Thus, some studies indicate histological or biochemical changes in theendometrium after treatment with ECPs. These studies permit theconclusion that ECPs may also interfere with the nidation of thefertilized egg in the endometrium^(1, 5, 6, 7).

More recent studies, however, contradict this assumption that theadministration of ECPs has effects on the endometrium^(1, 8, 9).

Further effects that are discussed include a disturbance in the functionof the corpus luteum, thickening of the cervical mucosa, which affectsthe entry of sperm, a change in the tubal transport of sperm and egg,and the direct inhibition of fertilization^(13, 10, 11, 12).

However, statistical data concerning the efficacy of ECPs indicate thatvarious factors contribute to the efficacy, and their effect is notattributable solely to the delay or prevention of ovulation¹⁴.

Some studies have shown that early treatment with ECPs that contain onlythe gestagen (levonorgestrel) has an effect both on the ovulatoryprocess and also on luteal function^(15, 18, 19, 20, 58). By contrast,two other studies show no effect on the endometrium^(16, 17).

Another study, in which the gestagen (levonorgestrel) was administeredbefore the LH surge, in turn shows an effect on the secretory pattern ofglycodelin in serum and endometrium²¹. However, this result could not beconfirmed in a later study whose very purpose was to assess endometrialglycodelin expression²².

A study of levonorgestrel carried out more than 30 years ago establishedan effect on the migration of the sperm and the function of the genitaltract²³. A more recent study indicated, however, that 1.5 mg oflevonorgestrel has no effects on the cervical mucosa or on the entry ofsperm into the uterine cavity²².

The reduced efficacy of EPCs when their administration is delayed afterunprotected sex suggests that EPCs have no effect on the nidation of theoocyte, since otherwise the efficacy of the product would probably notbe dependent on the time it was administered, at least as long as theECP is taken before nidation²⁴.

Studies on rats and capuchin monkeys (Cebus) with levonorgestrel in anovulation-inhibiting dose show that fertility is not impaired afterfertilization^(12, 25, 26). However, it is unclear whether thisobservation can be applied to humans.

Although the mechanism of action of ECPs is not entirely clear, it hasbeen demonstrated that ECPs have no abortive effect, even within themeaning of the definitions used by the medical authorities, e.g. theFood and Drug Administration/National Institutes of Health²⁷.

Besides the studies examining the mechanism of action, many studies haveexamined the suitability of different treatment regimens, gestagens anddoses for post-coital contraception. Post-coital contraception meansthat women who do not wish to become pregnant after unprotected sex takesuitable pharmaceutical products intended to prevent ovulation.

The first work in this connection was carried out as early as the 1970s.Thus, various gestagens, including levonorgestrel, were tested asroutine post-coital contraceptives in extensive studies (The Journal ofReproductive Medicine, 13 (2), (1974); Contraception, 7 (5), 367-379,(1973); Reproduction, 2 (1), 61-62, (1975); International Journal ofFertility, 20, 156-1 60, (1 975). The once a day doses were between 150μg and 1,500 μg. The results of the studies showed that the post-coitalcontraceptive efficiency of levonorgestrel, when used alone, was loweven at a dose of 1 mg.

A. A. Yuzpe and co-workers [The Journal of Reproductive Medicine 13 (2),(1974)] reported the results of such studies in which a pharmaceuticalcomposition containing 100 μg of ethinylestradiol and 1.0 mg ofnorgestrel was used as a post-coital contraceptive in a single dose. Thecomposition was taken within five days after unprotected sex. Thismethod was later modified. On the one hand, the period of time forpossible use of the composition was reduced from 5 days to 72 hours,and, on the other hand, the dose was doubled in the sense thatadministration of the composition was repeated 12 hours after the firstadministration [Fertility and Sterility, 28, 932-936, (1977); ibid. 37,508-51 3 (1982); International Journal of Gynaecology and Obstetrics,15, 133-1 36, (1977)]. This modification improved the success of themethod.

Following the studies by A. A. Yuzpe and co-workers, various othertrials were conducted to demonstrate the efficacy of this combination.In these studies, the total dose of ethinylestradiol was 0.2 mg,combined with 2.0 mg of norgestrel or 1.0 mg of levonorgestrel. Theresults of the studies showed that, although the above administration(Yuzpe regimen) caused fewer side effects than estrogens which were usedearlier at higher doses, the relative incidence of nausea and vomitingwas still very high (50% and 20% respectively). These side effects aredue to the estrogen effect and lead to reduced acceptance of the method.Moreover, the efficacy of the treatment decreases when vomiting occurs.

The use of levonorgestrel for emergency contraception was discovered inthe 90s. The results of the studies were reported in two well documentedpublications [Lancet, 352, 428-433, (1998), and Human Reproduction, 8(3), 389-392, (1993)]. The efficacy of tablets which contain only 0.75mg of levonorgestrel and of combination tablets from the Yuzpe methodwhich contain 0.1 mg of ethinylestradiol and 1.0 mg of levonorgestrelwas investigated within 48 hours and also within 72 hours afterunprotected sex, with the second dose being administered 12 hours afterthe first one. The results showed that the protection with two tabletsthat contain 0.75 mg of levonorgestrel was better than the protectionwith the Yuzpe regimen, and also that the women who received onlylevonorgestrel experienced fewer side effects, a finding that could beattributed to the absence of ethinylestradiol.

The results of the clinical studies also showed that the earlier thetreatment was started post coitus, the better the effect. However,experience shows that a woman will delay taking the first tablet inorder to avoid a situation where the second dose to be taken after 12hours falls at an unsuitable time (for example at a time when she willbe asleep). According to the studies, however, exact observance of the12-hour interval between the two doses is essential in order not toreduce the desired effect. According to statistical data, most of thewomen took the second dose within 12 to 16 hours after the first dose[Lancet, 352, 428-433, (1998)].

In view of the stated disadvantage (the delayed administration of the2nd tablet), European patent 1448207 describes a product that comprisesjust one tablet but contains twice the amount of levonorgestrel, i.e.1.5 mg of active substance. This tablet has to be taken within 72 hoursafter unprotected sex. As a clinical study was able to show, thecontraceptive effect is comparable to, or even slightly better than, thecontraceptive effect when the dose is divided into 2 tablets, eachcontaining 0.75 mg [E. Jonannson et al., Human Reproduction, vol. 17,no. 6, 1472-1476 (2002)]. Johannsen assumes, however, that the high-doseformulation of 1.5 mg will be more poorly tolerated (nausea, queasiness,vomiting, and also disturbance of the menstrual cycle).

Other research groups have investigated the influence of COX inhibitorson ovulation. For example, Pall et al. investigated the influence ofrofecoxib on ovulation [Pall et al.; Human Reproduction vol. 16, no. 7,pp 1323-1328 (2001)]. In this study, 25 mg of the active substance wereused on 9 successive days. A delay in ovulation of over 48 hours wasobtained in 4 of 6 patients.

The study by M. S. Bata et al. is in line with Pall's results butinvestigates the influence of meloxicam on ovulation [Bata et al., JClin Pharmacol (2006) 46:925-932]. This study shows that, with a dose of30 mg per patient and day (on 5 successive days), it is possible toachieve a delay in ovulation of 5 days.

Although COX inhibitors are known in principle as being relatively welltolerated, the EMEA [EMEA/62838/2005; EMEA/62757/2005] points to thisclass of substances as posing a higher risk of adverse cardiovascularevents, and it therefore recommends that the lowest effective dose beused. The currently available study data show a trend whereby the riskof renal and cardiovascular events increases as the selectivity forCOX-2 (cyclooxygenase type 2) increases. Meloxicam should therefore betreated with circumspection compared to other COX inhibitors such aspiroxicam [Clin Pharmacol Ther. 2009 February; 85 (2):190-7;Pharmacotherapy 2006; 26 (7):919-938]. Increasing COX-2 selectivity,however, is linked with lesser gastro-intestinal side effects, and theadverse cardiovascular events have hitherto been found only in cases ofchronic use [Am. J. Med. 2004; 117:100-106].

In a pilot study, Massai et al. investigated the use of meloxicam incombination with levonorgestrel (LNG) on the ovulation point inconnection with emergency contraception [Human Reproduction vol. 22, no.2, pp 434-439 (2007)]. In this study, 2 tablets were used, each onecontaining 0.75 mg of LNG (known, for example, by the trade namePostinor-2). Meloxicam was used at a dose of 15 mg. In the group ofpatients who had received the combination of meloxicam and LNG, therewas a trend toward a reduced incidence of ovulation compared to thegroup treated exclusively with LNG. This effect was increasingly morepronounced the later the tablets were taken relative to the ovulation.

The object of this invention is therefore to make available apharmaceutical composition for emergency contraception which can beadministered just once, with a reduced dose both of COX inhibitors andalso of gestagen, and which at the same time shows improvedcontraceptive efficacy compared to the currently availablegestagen-based contraceptive products. A further object of the inventionis to make available products which permit safe one-off use with reducedside effects and in which, in addition, COX inhibitors are used whichpose a minimal risk, or no risk, of cardiac and/or renal effects.

This object is achieved by the present invention. It was found that COXinhibitors potentiate the effect of gestagens, as a result of which thedose of gestagen required to avoid ovulation can surprisingly beconsiderably reduced. Conversely, gestagens can further potentiate theovulation-inhibiting effects of COX inhibitors. By means of thesesynergistic effects, it is possible, despite quite a low dosage,especially of the gestagen, to achieve a comparable or even enhancedcontraceptive effect and at the same time to reduce the side effects ofboth classes of substances.

Gestagen-associated side effects in particular (such as nausea andheadaches) can be reduced by addition of the COX inhibitor, whichincreases the tolerability and acceptance of the method.

It was also possible to show that the use of COX inhibitors also reducesthe rate of fertilization of ovulated cumulus-oocyte complexes (oocytesthat are surrounded by cumulus cells, where the cumulus cellssurrounding the oocyte have important functions in fertilization, TambaS. et al. PNAS 2008). That is to say, even if the ovulation is notsuppressed by COX inhibitors, there is a further contraceptive effectresulting from a reduced rate of fertilization. This is probably due toinfluences on the characteristics of the cumulus expansion which occursafter the LH peak and in which prostaglandins play a role (see Example3). This leads to improved reliability of contraception compared to theLNG-based market products that only use the mechanism of ovulationinhibition. Thus, improved efficiency of contraception is achieveddespite ovulation. Concerning the effect of prostaglandins on fertility,reference is made to the article by Normann R. J. THE LANCET 2001 andSirois J. et al. Human Reproduction Update, 2004.

It is also possible in principle to divide the dose of active substances(gestagen and COX inhibitor) in equal parts to 2 pills withoutsignificantly impairing the efficacy, as long as it is ensured that theinterval between the first dose and the second dose does not exceed 12hours, and as long as it is also ensured that both pills are takenwithin a period of 72 hours after unprotected sex. However, for thereasons mentioned in paragraph 24 (compliance in taking the second dose,and convenience for the patient), this form of administration is notpreferred.

As gestagen, it is possible in principle to use the gestagens that areknown and used in oral contraceptives and also other gestagens suitablefor oral use, e.g. chlormadinone acetate (CMA), norgestimate (NGM),norelgestromin (NGMN), norethisterone (NET)/norethisterone acetate(NETA), etonogestrel (3-keto-desogestrel), nomegestrol acetate (NOMAc),demegestone, promegestone, drospirenone (DRSP), medroxyprogesteroneacetate (MPA), cyproterone acetate (CPA), trimegestone (TMG),levonorgestrel (LNG), norgestrel (NG), desogestrel (DSG), gestodene(GSD) or dienogest (DNG), of which levonorgestrel (LNG), desogestrel(DSG), gestodene (GSD) and dienogest (DNG) are preferred. For the useaccording to the invention as a product for emergency contraception,levonorgestrel is particularly preferred.

The lower dose limit for the gestagen used for the emergencycontraception is a dose that still inhibits ovulation. This dose variesdepending on the gestagen used. The following suggested minimal dosesfor inhibition of ovulation (21-day use) are found in the literature(Table 1):

TABLE 1 Gestagen p.o. dose/day Chlormadinone acetate (CMA) 1.5-2 mg³³, 5mg³⁰ Cyproterone acetate (CPA) 1 mg³³ Desogestrel (DSG) 60 μg²⁸Dienogest (DNG) 1-2 mg²⁹ Drospirenone (DRSP) 2 mg³³ Dydrogesterone >30mg³³ Ethynodiol 2 mg³³ Gestodene (GSD) 30 μg³³, 40-50 μg²⁸Levonorgestrel (LNG) 50 μg³³, 60 μg²⁸ Lynestrenol 2 mg³³ Medrogestone 10mg³³ Medroxyprogesterone acetate (MPA) 10 mg³³ Nomegestrol acetate(NOMAc) 2.5 mg³² Norethisterone 0.5 mg³³ Norethisterone acetate (NETA)0.5 mg³³ Norgestimate (NGM) 180-250 μg³¹ Progesterone 300 mg³³Promegestone 0.5 mg³³ Trimegestone 0.5 mg³³

The upper dose limit for single administration of levonorgestrel is 900μg. According to the invention, a dose of 750 μg is preferred, i.e. anamount corresponding to half the dosage used in the emergencycontraception products on the market today, which are also all based onLNG.

For the other gestagens used according to the invention, the followingamounts indicate the dose ranges for preferred single administration:

TABLE 2 Dose p.o. (mg) Gestagen Minimum Maximum Chlormadinone acetate(CMA) 1.5 75 Cyproterone acetate (CPA) 1 15 Desogestrel (DSG) 0.06 0.9Dienogest (DNG) 1 30 Drospirenone (DRSP) 2 30 Dydrogesterone 30 450Ethynodiol 2 30 Gestodene (GSD) 0.03 0.75 Levonorgestrel (LNG) 0.05 0.9Lynestrenol 2 30 Medrogestone 10 150 Medroxyprogesterone acetate 10 150(MPA) Nomegestrol acetate (NOMAc) 2.5 37 Norethisterone 0.5 8Norethisterone acetate 0.5 8 (NETA) Norgestimate (NGM) 0.18 3.7Progesterone 300 4500 Promegestone 0.5 8 Trimegestone 0.5 8

According to the invention, dose ranges are particularly preferred thatcorrespond to twice the amount to six times the amount of anovulation-inhibiting dose. Therefore, according to the invention,particularly preferred dose ranges are 100-360 μg for levonorgestrel,1-12 mg for dienogest, 120-360 μg for desogestrel, 60-300 μg forgestodene, 3-30 mg for CMA, 360-1500 μg for NGM, and 5-15 mg for NOMAc.

Particular preference is given to a composition for emergencycontraception which, in addition to the COX inhibitor, containslevonorgestrel in an amount of 150-300 μg.

The COX inhibitors that are used according to the invention include inprinciple all the COX inhibitors that are available for otherindications, e.g. also meloxicam. COX inhibitors that are particularlysuitable according to the invention include piroxicam, naproxen,celecoxib, diclofenac, tenoxicam, nimesulide, lornoxicam andindomethacin, of which piroxicam is particularly preferred. Thus, thisCOX inhibitor in combination with a gestagen (LNG) has a better effectthan is achieved, for example, for the combination of LNG with meloxicam(see Example 1), and it additionally reduces fertilization.

For the COX inhibitors too, different dosages are to be employeddepending on the COX inhibitor used. Dose ranges for the COX inhibitorsused according to the invention result from the recommended maximumdaily doses of the respective COX inhibitor for preferably singleadministration. These recommended maximum doses relate to long-termtreatments and continuous therapies, and therefore, for the presentindication of emergency contraception with preferably a singleadministration, it is also possible to use three times the recommendedmaximum daily dose. A quarter of the recommended maximum daily dose isregarded as the lower limit. For the COX inhibitors used according tothe invention, this gives the following amounts (Table 3):

TABLE 3 Range for Recommended emergency maximum daily contraceptiondose* (mg) (mg) Piroxicam  20 5-60 Tenoxicam  40 10-120 Naproxen 1250 300-3800 Diclofenac 150 40-450 Indomethacin 200 50-600 Celecoxib 400100-1200 Nimesulide 200 50-600 Lornoxicam  16 4-48 Ibuprofen  2400**600-3600 *Maximum daily doses as per Wolters Kluver Health (Ovid SPVerlag) Drug Information Full Text **Maximum daily dose as per packinsert

In a preferred embodiment of the invention, a combination of piroxicamin a dose range of 5-60 mg and levonorgestrel in the range of 60-750 μgis used in the pharmaceutical formulation. Particular preference isgiven to a formulation containing 10-30 mg of piroxicam and 150 to 300μg of LNG.

The pharmaceutical formulation can be present in a solid or liquidstate, for example as a tablet, film-coated tablet or coated tablet,wafer, capsule, pill or powder. Lyophilized powder ampule formulations,which permit in situ preparation of liquid compositions, are alsoincluded. Liquid compositions can be injection solutions or infusionsolutions, for example.

The preparation of the pharmaceutical formulation is familiar to anexpert. The preparation of a formulation as a tablet is described inExample 4.

The efficacy of the composition according to the invention wasascertained by ovulation-inhibiting studies carried out on adult femalerats with normal cycles. First, using 5 dose groups plus placebo (0.003mg, 0.01 mg, 0.03 mg, 0.1 mg and 0.3 mg), the limit dose oflevonorgestrel (LNG) was determined at which there is still noovulation-inhibiting effect. It was found that a dose of 0.01 mg oflevenorgesterel per animal (subcutaneous, hereinafter abbreviated tos.c.) still has no ovaulation-inhibiting effect.

With the dose of LNG thus determined (0.01 mg), a comparison test wasthen carried out in which the ovulation-inhibiting effect of LNG,placebo, meloxicam, piroxicam, and the combination of LNG and meloxicam,was compared against the composition, according to the invention, of LNGplus piroxicam.

With the onset of the metestrus, 5 animals in each case were treated onfour successive days with (a) placebo, (b) 0.01 mg of LNG, (c) 2 mg ofpiroxicam, (d) 0.01 mg of LNG and 2 mg of piroxicam, (e) 2 mg ofmeloxicam, and (f) 0.1 mg of LNG and 3 mg of meloxicam. LNG was given bys.c. administration, and the COX inhibitor was given orally (p.o.).

Whereas 42 oocytes ovulated in control group (a) and 35 oocytes ovulatedin treatment group (b) with 0.1 mg of levonorgestrel, the ovulation ratewith a combination of 2 mg p.o. of piroxicam plus 0.1 mg oflevonorgestrel (treatment group d) was only 3 oocytes (only one animalof 5 showed any ovulation at all). By contrast, with 2 mg of piroxicamon its own (treatment group c), 9 oocytes ovulated.

At a still lower dose of just 1 mg of piroxicam, the ovulation rate forthe combination with 0.1 mg of levonorgestrel was 16 oocytes, whereas 1mg of piroxicam allowed 28 oocytes to ovulate.

The comparison between LNG/meloxicam and LNG/piroxicam and LNG showsthat meloxicam plus LNG in this direct comparison is less effective thanpiroxicam plus LNG. Thus, a combination of 2 mg of meloxicam plus 0.01mg of levonorgestrel still showed an ovulation rate of 18 oocytes in 5animals.

In another test (Example 2) on rats (n=10 animals) with intact menstrualcycles, it was surprisingly found that piroxicam on its own has asignificant dose-dependent effect on the serum progesteroneconcentration on the evening (19.00 h) of the proestrus, i.e. at thetime of the LH peak. This can be seen as an indicator of the efficiencyof the LH peak in changing from a predominantly estrogen-producing ovary(before the LH peak) to a predominantly progesterone-producing ovary(caused by the LH peak). This surprising finding shows that piroxicam onits own has an effect on the hormonal situation, which can result in acontraceptive effect or in an increase of a contraceptive effect of agestagen. By contrast, the literature describes that other COXinhibitors have no effect on the hormonal levels [Pall et al.; HumanReproduction vol. 16, no. 7, pp 1323-1328 (2001); Bata et al., J ClinPharmacol (2006) 46:925-932]. In this test too, it was found that thecombination of low-dose levonorgestrel (0.01 mg s.c.) with piroxicam(0.5; 1 and 2 mg p.o.) inhibits ovulation considerably better than eachsubstance on its own: 100 oocytes ovulated in the vehicle group, 68 inthe group with LNG on its own, 85 in the group with 0.5 mg of piroxicam,56 in the group with 1 mg of piroxicam, and 30 in the group with 2 mg ofpiroxicam. The ovulation rates in the combination with 0.01 mg oflevonorgestrel and 0.5 mg of piroxicam (31 oocytes), with 1 mg ofpiroxicam (19 oocytes) and with 2 mg of piroxicam (0 oocytes) were muchlower here and, in the highest dose, even led to complete anovulation(10 animals per group).

The invention is explained by the following nonlimiting examples.

EXAMPLE 1 Ovulation Inhibition Test on Rats

The rat is an especially suitable animal model for demonstration ofovulation-inhibiting substances, since it ovulates spontaneously and themenstrual cycle can be easily monitored using vaginal smears.

In the following test, female rats weighing between 200 and 220 g wereused. The animals were housed in macrolon cages in rooms undercontrolled lighting conditions (12 hours of darkness, 12 hours oflight), were fed a standard diet and had access to water ad libitum.

Levonorgestrel was dissolved in benzyl benzoate/castor oil (1+4 v/v),and the daily dose was given by s.c. administration in a volume of 1ml/kg body weight.

The COX inhibitors were suspended in a carrier liquid (85 mg of MyrjR53(2-hydroxyethyl octadecanoate; CAS no. 9004-99-3) in 100 ml of 0.9% w/vNaCl solution), and the daily dose corresponding to the treatment groupwas administered orally in a volume of 2 ml/kg body weight.

Two cycles were monitored using vaginal smears before the start of thetest. Only animals with a regular 4-day cycle were entered in the test.The allocation to the treatment groups was randomized. Starting in themetestrus, the test substance was administered for 4 days (days 1-4) andthe cycle continued to be monitored. On day 3 of treatment (proestrus),a retrobulbar blood sample was taken at 9.00 h and from 18.30 h in orderto determine the luteinizing hormone (LH). On day 4 (afteradministration), the animals with vaginal smears showing them in estrusor metestrus underwent unilateral ovariectomy under anaesthetic. Crushpreparations were made from the tubes and were examined under amicroscope for the presence of oocytes. On day 5, all the animals (theintact animals and those having undergone unilateral ovariectomy) weresacrificed, and the tubes of the animals in estrus and metestrus wereprepared and examined in the same way. The tests that were carried outshow that a low dose of levonorgestrel, although not itself inhibitingovulation, does provide increased suppression of ovulation when combinedwith COX inhibitors, and, in the case of piroxicam, almost completesuppression of ovulation can be achieved. By contrast, the COXinhibitors on their own provide only partial suppression of ovulation.

The results of the study, i.e. the combined effect of levonorgestrelplus COX inhibitors on ovulation, are summarized in Table 4:

TABLE 4 Ovulation count, Ovulation count, Treatment group absolute meanVehicle 42 8.4 ± 0.5 LNG 0.01 mg s.c. 35 7.0 ± 2.0 Meloxicam 2 mg p.o.28 5.6 ± 2.5 Piroxicam 2 mg p.o. 9 1.8 ± 0.4 LNG (0.01 mg) + Priox 3 0.6± 1.3 (only 1 (2 mg) animal ovulated 3 oocytes) LNG (0.01 mg) + Melox 183.6 ± 3.3 (2 mg)

EXAMPLE 2

The test set-up corresponds to the one described in Example 1.

The results for the progesterone concentrations in proestrus at 19.00 hare summarized in Table 5:

TABLE 5 Progesterone in proestrus at Treatment group 19.00 h - mean ± SD(n = 10) Vehicle 254 ± 88 Piroxicam 0.5 mg p.o. 237 ± 49 Piroxicam 1 mgp.o. 183 ± 67 Piroxicam 2 mg p.o. 122 ± 94

EXAMPLE 3

Substances can influence fertility by reducing the fertilizability ofoocytes or cumulus-oocyte complexes. In order to investigate sucheffects, substances can be administered in vivo and, after ovulationfrom cumulus/oocyte complexes, can be subjected to in vitrofertilization. The in vitro fertilization rate, with no further testsustance being added, allows conclusions to be drawn regarding the invivo effects of the test sustances.

Immature female mice (strain: B6D2F1, Charles River, Suelzfeld, age:19-25 days) were housed in macrolon cages in rooms under controlledlighting conditions (12 hours of darkness, 12 hours of light), were feda standard diet and had access to water ad libitum.

The mice were primed with PMSG (Pregnant Mare Serum Gonadotropin) (10IU/animal i.p.). After 48 hours, an ovulation-triggering stimulus wasinduced in the animals by administration of 10 IU/animal i.p. The COXinhibitors were suspended in a carrier liquid (85 mg MyrjR53(2-hydroxyethyl octadecanoate; CAS no. 9004-99-3) in 100 ml of 0.9% w/vNaCl solution), and the daily dose corresponding to the treatment group(n=5 animals per group) was administered in a volume of 0.2 ml p.o. 8hours before and together with hCG. Fourteen hours after hCGadministration, the animals were sacrificed. Ovulated oocytes andcumulus-oocyte complexes were recovered from the ovarian bursa and/oroviduct and subjected to in vitro fertilization, with a sperm count of40,000 sperm/0.5 ml for 1 hour being used for the fertilization.Twenty-four hours after incubation with the sperm, the number offertilized oocytes was established and the percentage fertilization ratedetermined.

The results show that piroxicam has an effect on the fertilizability ofovulated cumulus-oocyte complexes.

The results of the study of the effect of piroxicam on the fertilizationrate of ovulated cumulus-oocyte complexes are summarized in Table 6:

TABLE 6 Fertilization Treatment group rate (% ± SD) Vehicle 55 ± 16Piroxicam (2 × 0.5 mg/ 12 ± 7  animal p.o.) Piroxicam (2 × 0.3 mg/ 14 ±18 animal p.o.) Piroxicam (2 × 0.15 mg/ 19 ± 8  animal p.o.)

EXAMPLE 4 Method for Producing a Tablet for Emergency Contraception

Tablets having a total weight of 200 mg per tablet and being of thecomposition shown in Table 7

TABLE 7 Levonorgestrel, micronized  0.25 mg Piroxicam, micronized 20.00mg Lactose monohydrate 107.75 mg  Maize starch 36.00 mg Modified starch24.00 mg Polyvinylpyrrolidone 25000 10.00 mg Magnesium stearate  2.00 mgwere produced by filling a fluidized bed granulator with 31.68 kg ofmaize starch, 21.12 kg of modified starch, 0.22 kg of levonorgestrel(micronized), 17.6 kg of piroxicam (micronized) and 94.82 kg of lactosemonohydrate and by activating the fluidized bed. An aqueous solution of8.8 kg of polyvinylpyrrolidone 25000 in 50 kg of purified water wassprayed continuously onto the fluidized bed, and the mixture was driedat the same time by heating the air stream of the fluidized bed. At theend of the process, 1.76 kg of magnesium stearate were introduced intothe fluidized bed granulator and mixed with the resulting granules withthe fluidized bed running. The granulate thus formed was pressed in arotary tablet press into the shape of a tablet with an 8 mm diameter.

LITERATURE

-   1. Swahn M L. Effect of post-coital contraceptive methods on the    endometrium and the menstrual cycle. Acta Obstet Gynecol Scand 1996;    75:738-44.-   2. Ling W Y. Mode of action of dl-norgestrel and ethinylestradiol    combination in postcoital contraception. Fertil Steril 1979;    32:297-302.-   3. Rowlands S. A possible mechanism of action of danazol and an    ethinylestradiol/norgestrel combination used as postcoital    contraceptive agents. Contraception 1986; 33:539-45.-   4. Croxatto H B. Effects of the Yuzpe regimen, given during the    follicular phase, on ovarian function. Contraception 2002; 65:121-8.-   5. Kubba A A. The biochemistry of human endometrium after two    regimens of postcoital contraception: a    dl-norgestrel/ethinylestradiol combination or danazol. Fertil Steril    1986:45:512-6.-   6. Ling W Y. Mode of action of dl-norgestrel and ethinylestradiol    combination in postcoital contraception. II. Effect of postovulatory    administration on ovarian function and endometrium. Fertil Steril    1983; 39:292-7.-   7. Yuzpe A A. Post coital contraception—a pilot study. J Reprod Med    1974; 13:53-8.-   8. Taskin O. High doses of oral contraceptives do not alter    endometrial α1 and ανβ3integrins in the late implantation window.    Fertil Steril 1994; 61:850-5.-   9. Raymond E G. Effect of the Yuzpe regimen of emergency    contraception on markers of endometrial receptivity. Hum Reprod    2000; 15:2351-5.-   10. Ling W Y. Mode of action of dl-norgestrel and ethinylestradiol    combination in postcoital contraception. III. Effect of preovulatory    administration following the luteinizing hormone surge on ovarian    steroidogenesis. Fertil Steril 1983; 40:631-6.-   11. Croxatto H B. Mechanism of action of hormonal preparations used    for emergency contraception: a review of the literature.    Contraception 2001; 63:111-21.-   12. Croxatto H B. Mechanisms of action of emergency contraception.    Steroids 2003; 68:1095-8. 5-   13. Glasier A. Emergency postcoital contraception. N Engl J Med    1997; 337:1058-64.-   14. Trussell J, Raymond E G. Statistical evidence concerning the    mechanism of action of the Yuzpe regimen of emergency contraception.    Obstet Gynecol 1999; 93:872-6.-   15. Hapangama D. The effects of peri-ovulatory administration of    levonorgestrel on the menstrual cycle. Contraception 2001; 63:123-9.-   16. Durand M. On the mechanisms of action of short-term    levonorgestrel administration in emergency contraception.    Contraception 2001; 64:227-34.-   17. Marions L. Emergency contraception with mifepristone and    levonorgestrel: mechanism of action. Obstet Gynecol 2002; 100:65-71.-   18. Marions L, Cekan S Z, Bygdeman M, Gemzell-Danielsson K. Effect    of emergency contraception with levonorgestrel or mifepristone on    ovarian function. Contraception 2004; 69:373-7.-   19. Croxatto H B. Pituitary-ovarian function following the standard    levonorgestrel emergency contraceptive dose or a single 0.75-mg dose    given on the days preceding ovulation. Contraception 2004;    70:442-50.-   20. Okewole I A. Effect of single administration of levonorgestrel    on the menstrual cycle. Contraception 2007; 75:372-7.-   21. Durand M. Late follicular phase administration of levonorgestrel    as an emergency contraceptive changes the secretory pattern of    glycodelin in serum and endometrium during the luteal phase of the    menstrual cycle. Contraception 2005; 71:451-7.-   22. Nascimento J A. In vivo assessment of the human sperm acrosome    reaction and the expression of glycodelin-A in human endometrium    after levonorgestrel emergency contraceptive pill administration.    Hum Reprod 2007; 22:2190-5.-   23. Kesserü E. The hormonal and peripheral effects of dnorgestrel in    postcoital contraception. Contraception 1974; 10:411-24.-   24. Trussell J. Plan B and the politics of doubt. J Am Med Assoc    2006; 296:1775-8.-   25. Müller A L. Postcoital treatment with levonorgestrel does not    disrupt postfertilization events in the rat. Contraception 2003;    67:415-19.-   26. Ortiz M E. Postcoital administration of levonorgestrel does not    interfere with post-fertilization events in the new-world monkey    Cebus apella. Hum Reprod 2004; 19:1352-6.-   27. Hatcher R A, Trussell J. Emergency Contraception: The Nation's    Best Kept Secret. Decatur G A: Bridging the Gap Communications,    1995.-   28. Teichmann “Empfängnishütung: eine vergleichende Übersicht aller    Methoden, Risiken and Indikationen”, published by Georg Thieme    Verlag (1996)-   29. Moore C, Carol W, Gräser T et al. in Clin Drug Invest 18,    271-8 (1999) Influence of dienogest on ovulation in young fertile    women-   30. R. Druckmann; contraception 79 (2009) 272-281: Profile of    progesterone derivative chlormadinone acetate—Pharmacodynamic    properties and therapeutic applications-   31. Fertility control Stephen L. Corson, Richard J. Derman,    Louise B. Tyrer Edition: 2, illustrated. Publishers Taylor &    Francis, 1994 ISBN 096979780X, 9780969797807 514 pages-   32. Bazin B, Thevenot R, Bursaux C and Paris J (1987) Effect of    nomegestrol acetate, a new 19 nor-progesterone derivative, on    pituitary-ovarian function in women. Br J Obstet Gynaecol 94,    1199-1204-   33. Schindler A. E. et al (2003) Classification and pharmacology of    progestins Maturitas 46, S1, 7-16

The invention claimed is:
 1. A pharmaceutical composition comprising (a)50-900 μg levonorgestrel; (b) 5-60 mg piroxicam; and (c) apharmaceutically acceptable excipient; the pharmaceutical compositionbeing adapted for oral administration in a single dose to preventpregnancy.
 2. The pharmaceutical composition as claimed in claim 1,comprising levonorgestrel in a dose of 100-360 μg.
 3. The pharmaceuticalcomposition as claimed in claim 1, comprising levonorgestrel in a doseof 150-300 μg.
 4. A method for emergency contraception comprisingadministering to a patient in need thereof a composition comprising thecomposition of claim
 1. 5. The method of claim 4, wherein thepharmaceutical composition is administered in a single dose within 72hours post coitus.